Fabric wipes having color indicators are disclosed in U.S. Pat. No. 4,311,479, issued to Fenn et al., and in U.S. Pat. No. 4,678,704, issued to Fellows. Fenn et al. discloses a cloth impregnated with an antimicrobial composition that is activated upon contact with a liquid such as water, and is ionically bonded to the cloth. Small portions of the impregnated cloth are dyed with an indicator dye which bonds preferentially to the antimicrobial composition so that when the antimicrobial composition is exhausted, the dye will disappear from the cloth.
Fellows discloses an impregnated fabric material having an active cationic impregnant bonded to its fabric substrate. An anionic indicator dye in combination with a further cationic component is also bonded to the substrate. The dye bonds to the further cationic component more readily than to the substrate and the further cationic component competes with the impregnant for bonding to the dye. In the case of a wiping cloth, when the dye has been removed to indicate exhaustion of the active component, enough active component remains on the cloth to provide a safety margin.
While these and similar prior art fabrics had color indicators to indicate the dissipation of impregnant, the indicators only worked once, and only changed color once. If the fabric was then recharged with impregnant, such as by dipping it into a bucket, the original color would not return and the indicator function would not return.
There is a need or desire for fabrics impregnated with cleansing solutions, disinfectants and the like which can be recharged multiple times for multiple uses, and which indicate each time when the level of cleansing solution or disinfectant becomes low.